Neodymium doped Na{hd 2{b O{HU .{B P{HD 2{B O{HD 5{B -ZnCl{hd 2{b glass exhibiting fluorescence at 1.06 micrometers

ABSTRACT

A novel glass exhibits fluorescence from trivalent neodymium ions at a wavelength of approximately 1.06 micrometers. The glass consists essentially of 98 to 99 weight percent of a host glass and 1 to 2 weight percent of a compound which contributes trivalent neodymium ions to the glass. The host glass consists essentially of 30 to 50 mol percent of Na2O.P2O5 and 50 to 70 mol percent of ZnCl2. The compound is selected from a group consisting of Nd2O3, NdF3, and NdCl3.

States 511 tet 1 1 Shaw et al. I

[ Mar. 4, 1975 NEODYMIUM DOPED Na O -P O -ZnC1 GLASS EXHIBITINGFLUORESCENCE AT 1.06 MICROMETERS [75] Inventors: Robert R. Shaw,Sturbridge; Elias Snitzer, Wellesley, both of Mass.

[73] Assignee: American Optical Corporation,

Southbridge, Mass.

[22] Filed: Jan. 11, 1973 [21] App]. No.: 322,678

[521 US. Cl 252/301.6 P, 106/47 Q, 331/945 E [51} Int. Cl C09k l/06,C03c 3/28, C03c 3/16 [58] Field ofSearch...252/30l.6 R, 301.6 P, 301.4P,

252/301.4 R; 106/47 Q, 47 R [56] References Cited UNITED STATES PATENTS3.580.859 5/1971 Buzhinsky et a1. 252/3014 P OTHER PUBLICATIONS Schulz,I. Naturwissenschaften, Vol. 44, (1957), p.

536, Zinkehlorid als Glasbidner.

Ranson, H. Inorganic Glass-Forming Systems (1967), Academic Press, NY.TP857R3, p. 164,

Primary Examiner-Winston A. Douglas Assistant E.\'aminerMark BellAttorney, Agent, or FirmWil1iz1im C. Nealon [57] ABSTRACT 6 Claims, 1Drawing Figure PATENTED MR 4 75 WIMBISQOEQZ \S RELATIVE lNTENSITYNEODYMIUM DOPED NA O'P O -ZNCL GLASS EXHIBITING FLUORESCENCE AT 1.06MICROMETERS BACKGROUND OF THE INVENTION This invention is related tonovel glasses and is more particularly concerned with such glasses whichexhibit fluorescence when doped with trivalent neodymium ions.

In recent years, the glass laser has become an extremely important classof lasers. The glasses are doped generally with trivalent rare earthions. Predominant among these rare earth ions is the neodymium ion.Glass lasers doped with trivalent neodymium ions are capable ofgenerating very high power outputs at relatively high efficiencies.

Glass has various characteristics which make it an ideal laser hostmaterial. It can be made in large pieces of diffraction-limited opticalquality, e.g. with an index of refraction variation of less than 1 partper million across a 2.5 centimeter diameter. In addition, glass lasershave been made in a variety of shapes and sizes from fibers of a fewmicrons diameter supporting only a single dielectric waveguide mode, torods which are 2 meters long and 7.5 centimeters in diameter.Furthermore, pieces of glass with quite different optical properties canbe fused to solve certain system design problems. For example, glasscompositions can be varied in order to acquire an index of refractionvarying throughout the range of from 1.5 to 2.0. Therefore, thoseskilled in the art are constantly searching for new glassy materialswhich can serve as viable hosts for the trivalent neodymium laser ions.This is done in order to enlarge the spectrum of physical, optical, andchemical properties in order to provide a glass material totallycompatible with the designers system requirements.

When searching for such viable host materials, it is characteristic toexamine the fluorescence spectrum exhibited by the host material whendoped with the trivalent neodymium ions. When one acquires such a hostmaterial, it is highly probable that an operable laser material can beformed of the new glass. The limitations on this generally revolvearound the ability to manufacture the glass in sufficient quantity andof sufficient optical quality.

SUMMARY OF THE INVENTION Accordingly, it is an object of the presentinvention to provide novel laser materials which exhibit fluorescence atthe characteristic wavelength, 1.06 micrometers, generally associatedwith the trivalent neodymium ion.

Briefly, the invention in its broadest aspect comprises a glassconsisting essentially of 98 to 99 weight percent of a host glassconsisting essentially of 30 to 50 mol percent of Na O.P O and 50 to 70mol percent of ZnCl and l to 2 weight percent of a compound contributingtrivalent neodymium ions where the compound is selected from a groupconsisting of Nd O NdF and NdCl Further objects, advantages, andfeatures of the invention will be'apparent from the following detaileddescrlptinn of the invention.

DESCRIPTION OF THE DRAWING In the drawing, the sole FIGURE is agraphical representation of a typical fluorescence spectrum of a glassaccording to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawing, atypical fluorescence spectrum curve is shown. The curve shows two peaks,at approximately 1.06 micrometers and at approximately 0.9 micrometers.The peak at 1.06 micrometers is generally the most important in glassesdoped with neodymium. The peaks have relative intensity values A and B,associated with the peaks at 0.9 and 1.06 micrometers, respec tively.

The fluorescence curves shown. were measured in a Cary 14spectrophotometer by placing the glass samples in a copper fixture whichin turn were placed in the sample compartment of the Cary. The glass wasirradiated at right angles with a Xenon arc lamp through a filter whichblocked the transmission of wavelengths longer than approximately 800nm. The fluorescent spectrum was recorded using the automatic slitcontrol which adjusted the slit width so that the output of a coiledtungsten filament lamp with a filament temperature of approximately2800K produced a constant deflection on the recording chart for allwavelengths. Thus the recording chart must be corrected to obtain thetrue relative intensities by dividing the chart deflection by a factorproportional to the energy radiated by .the tungsten lamp at thewavelengths of interest. We have estimated the correction factor to beapproximately unity at the wavelengths of interest. This estimate wasmade by using the tungsten emissivities mea-' sured by J. C. DeVos (J.C. DeVos, Physics 20,690( 1954) for a ribbon filament tungsten lampoperating at 2800K in a calculation of the energy radiated by the coiledfilament lamp at the two wavelengths of interest. The intensity ratiosreported here were measured directly from the Cary charts using nocorrection factor.

Several examples of glasses according to the present invention are givenin the following examples. Each of these glasses was formed inapproximately a 50 gram melt. The glass is preferably formed in thefollowing manner. The components were added to the batch as the finalconstituents and were added in the known stoichiometric amounts to yielda glass having a final composition as given in the following examples.The glass making materials must be of high purity and, in particular,must be free of contamination from iron or other elements which wouldcause light absorption at the primary fluorescence wavelength, 1.06micrometers, if present in the glass. The finished glass, for example,should not contain more than 5 parts per million of iron as Fe O Theglass may be prepared by fusing the raw materials in a platinum crucibleheated in a Globar electric furnace, an RF induction coil, or a gasflame. No special atmosphere was necessary in the furnace. The rawmaterials were mixed intimately and as completely as possible in amixing device that does not introduce any contamination. The mixed batchwas loaded into a platinum crucible which did not contaminate the meltwith undesired impurities. The crucible was raised to a meltingtemperature of ll00C. The batch was held at this temperature forapproximately 15 minutes for the 50 gram samples. During this time, themelt was stirred with a platinum rod. The glass was then cast onto aniron plate at room temperature. It is to be understood that largersamples require a different procedure.

EXAMPLE 1 A glass which consists of about 99 weight percent of a hostglass and about 1 weight percent of NdCl has values for A and B of 0.40and 0.74 respectively on the fluorescent emission spectrum. Thecomposition, in mol percent, of the host glass is essentially Nap-P 30zncl 70 EXAMPLE 2 A glass which consists of about 98 weight percent of ahost glass and about 2 weight percent of Nd O has values for A and B of0.51 and 1.04 respectively on the fluorescent emission spectrum. Thecomposition, in mol percent, of the host glass is essentially NH OP O 40Znci 60 EXAMPLE 3 A glass which consists of about 98 weight percent of ahost glass and about 2 weight percent of NdCl has values for A and B of0.36 and 0.66 respectively on the fluorescent emission spectrum. Thecomposition, in mol percent, of the host glass is essentially Na O'P O40 zncl 6O EXAMPLE 4 Na O'P O 50 ZnCl 50 EXAM PLE 5 A glass whichconsists of about 99 weight percent of a host glass and about 1 weightpercent of NdF has values for A and B of 0.42 and 0.87 respectively onthe fluorescent emission spectrum. The composition, in mol percent, ofthe host glass is essentially The invention may be embodied in otherspecific forms without departing from the spirit or essentialcharacteristics thereof. The present embodiments are therefore to beconsidered in all respects as illustrative and not restrictive, thescope of the invention being indicated by the appended claims ratherthan by the foregoing description, and all changes which come within themeaning and range of equivalency of the claims are therefore intended tobe embraced therein.

What is claimed is:

l. A glass which exhibits fluorescence at a wavelength of 106 umconsisting essentially of 98 to 99 weight percent of a host glassconsisting essentially of 30 to 50 mol percent of Na2O.P2O5 and 50 tomol percent of ZnCl and l to 2 weight percent of a compound contributingtrivalent neodymium ions where the compound is selected from a groupconsisting of Nd203, and NdCl3.

2. A glass according to claim 1, wherein the host glass has essentiallythe following composition as given in mol percent and wherein thecompound contributing trivalent neodymium ions is NdCl and is present inan amount of about 1 weight percent.

3. A glass according to claim 1, wherein the host glass has essentiallythe following composition as given in mol percent and wherein thecompound contributing trivalent neodymium ions is Nd O and is present inan amount of about 2 weight percent.

4. A glass according to claim 1, wherein the host glass has essentiallythe following composition as given in mol percent and wherein thecompound trivalent neodymium ions is NdCl and is present in an amount ofabout 2 weight percent.

5. A glass according to claim 1, wherein the host glass has essentiallythe following composition as given in mol percent and wherein thecompound contributing trivalent neodymium ions is NdCl and is present inan amount of about 2 weight percent.

6. A glass according to claim 1, wherein the host glass has essentiallythe following composition as given in mol percent and wherein thecompound contributing trivalent neodymium ions is NdF and is present inan amount of about 1 weight percent.

1. A GLASS WHICH EXHIBITS FLUOROESCENCE AT A WAVELENGTH OF 1.06 UMCONSISTING ESSENTIALLY OF 98 TO 99 WEIGHT PERCENT OF A HOST GLASSCONSISTING ESSENTIALLY OF 30 TO 50 MOL PERCENT OF NA2OP2O5 AND 50 TO 70MOL PERCENT OF ZNCL2 AND 1 TO 2 WEIGHT PERCENT OF A COMPOUNDCONTRIBUTING TRIVALENT NEODYMIUM IONS WHERE THE COMPOUND IS SELECTEDFROM A GROUP CONSISTING OF ND2O3, NDF3 AND NDCL3.
 2. A glass accordingto claim 1, wherein the host glass has essentially the followingcomposition as given in mol percent
 3. A glass according to claim 1,wherein the host glass has essentially the following composition asgiven in mol percent
 4. A glass according to claim 1, wherein the hostglass has essentially the following composition as given in mol percent5. A glass according to claim 1, wherein the host glass has essentiallythe following composition as given in mol percent
 6. A glass accordingto claim 1, wherein the host glass has essentially the followingcomposition as given in mol percent